Thrust controlling apparatus

ABSTRACT

Apparatus comprises elongate shroud surrounding all or part of jet engine. Aft portion of shroud extends rearward beyond exit end of jet nozzle to surround and control exhaust gas stream. Continuous peripheral passage or several discrete passages through shroud wall aft of nozzle exit provide flow paths for entry of free stream air to constitute aft portion of shroud an ejector barrel and for exit of exhaust gas stream to constitute aft portion of shroud a thrust reverser. Blocker doors, generally triangular in planform, are circumferentially spaced around interior of barrel with their bases pivotally mounted in the barrel and their apices pivotally mounted in a common mounting at the longitudinal axis of the shroud and forward of the base mountings so that the axes of rotation of the doors are disposed along radial planes from the engine axis and converge forward. Each door in stowed position lies in a plane containing the longitudinal axis of the shroud and rotates approximately 90* to fully deployed position in a transverse plane wherein the doors form a forwardly convex cone to block axial rearward flow and direct engine gases out through passages. Control ring is mounted in barrel in plane of base mounting of the doors for limited rotative movement of ring about engine axis, and is linkconnected to doors to rotate them about their axes. Actuator in barrel rotates control ring and can retain ring in any intermediate position for modulated thrust reversal.

llmted States Patent 1 1 3,685,737

Ronald 1451 Aug. 22, 1972 [54] THRUST CONTROLLING APPARATUS [57] ABSTRACT lllventofl Christopher Ronald, mp l Apparatus comprises elongate shroud surrounding all Beach, Callfor part of jet engine. Aft portion of shroud extends [73] Assignee: Rohr Corporation, Chula Vista, rearward beyond em end of Jet to suyround Calm and control exhaust gas stream. Continuous peripheral passage or several discrete passages through shroud Flledi p 1970 wallaft of nozzle exit provide flow paths for entry of [21] Appl No: 71,527 free stream air to constitute aft portion of shroud an ejector barrel and for exit of exhaust gas stream to constitute aft portion of shroud a thrust reverser.

[52] US. Cl. ....239/265.19, 239/265.29, 239/265.39 Blocker doors, generally triangular in planform, are

[ llltsun-1363b 11/ 640- l circumferentially spaced around interior of barrel with [58] Field of Search ..239/265.l9, 265.33, 265.37, their bases pivotally mounted in the barrel and their 239/265.39, 265.43, 265.25, 265.27 apices pivotally mounted in a common mounting at the'longitudinal axis of the shroud and forward of the [56] References Cited base mountings so that the axes of rotation of the 1 doors are disposed along radial planes from the engine UNlTED STATES PATENTS axis and converge forward. Each door in stowed posi- 3,113,428 12/1963 Colley e161 ....239 265.27 tien lies in a plane containing the longitudinal axis of 2,944,395 7/1960 Doak ..239/265.29 the Shroud and rotates approximately to fully 2,955,417 11/1960 Brown ..239/265.27 p oy position in a transverse Plane wherein the 3,068,646 12/1962 Fletcher ..239/265.29 deers form a forwardly eenvex cone to block axial 3,095,697 7/1963 Reinhart ..239/265.'27 rearward flew and direct engine easeS out through 3 92 321 2 1970 Monaghan et 1 239 2 5 29 passages. Control ring is mounted in barrel in plane of Primary Examiner-Lloyd L. King AttorneyGeorge E. Pearson base mounting of the doors for limited rotative movement of ring about engine axis, and is link-connected to doors to rotatethem about their axes. Actuator in barrel rotates control ring and can retain ring in any intermediate position for modulated thrust reversal.

19 Claims, 6 Drawing Figures PATENTEflAuszz 1912 3.685737 SHEET 1 OF 2.

v 3 J INVENTOR.

CHRISTOPHERC. RONALD F|G.2. I BY ATTORNEY PATENTEDAUBZZ m2 3.685.737

. INVENTOR.

CHRISTOPHER C. RONALD ATTORNEY TI-IRUST CONTROLLING APPARATUS BACKGROUND OF THE INVENTION This invention lies in the field of gasturbine engines, which produce reaction thrust by ejecting a high velocity stream of gas from the exhaust nozzle or tail pipe of the gas turbine. Jet airplanes have very high landing speeds along with residual thrust from the engines. This places an excessive burden on the wheel brakes unless, some retarding means is provided to assist in deceleration. In addition, the operation of military airplanes in steep dives or carrier landing approaches requires a high degree of speed braking in flight, frequently followed by a need for immediate full power application. The invention is directed to apparatus which increases mass flow by mixing free stream air with the gas stream and apparatus which reverses the direction of exhaustflow to produce counter thrust and is more particularly directed to combined apparatus which performs-both'of these functions. Various schemes have been proposed and tested to solve the problem and have met with some success. However, they all suffer various drawbacks such as relative inefficiency, complication, weight, or excessive maintenance requirements. v

SUMMARY OF THE INVENTION This invention provides a very satisfactory solution to the general problem and offers a combination apparatus consisting of an ejector which induces the free stream air into a mixing zone with the exhaust gas stream, the ejector inlet passages also serving as outlet passages when in the reverse thrust mode. A plurality of blocker doors are providedwhich may be precisely adjusted to positions which block part or all of the exhaust gases and redirect them forward and out of the ejector ports.

Generally stated, in generic form, the apparatus pivotal axis to lie in a plane generally transverse to the engine axis. The doors are of such size and shape that,

in fully deployed position, their side edges are substantially in contact and they cooperate to define a forwardly convex blocking cone. To insure substantially complete flow blockage, the bases of the doors are curved to conform to the contour of the inner wall of the ejector barrel when they are fully deployed.

In stowed position the doors are, in effect, straight fore and aft vanes which tend to straighten the rotating exhaust gas flow. Adjoining doors swing in opposite angular senses as they deploy, thus avoiding any tendency to impose rotation on the gas stream. A control ring in the barrel rotates about the shroud axisvand is connected by linkages to the doors to cause their rotation. An actuator in the barrel rotates the ring and is adj ustable to any position between stowed anddeployed position to produce any desired degree of modulated or partial blocking. The forwardly convex cone defined by the-deployeddoors diverts the gas stream rearvvardly and laterally to the inner ends of the passages and cooperates with the passages to reverse the exiting gas flow while greatly reducing turbulence and stagnation pockets.

BRIEF DESCRIPTION OF THE DRAWINGS junction with the accompanying drawings, in which:

comprises an elongate streamlined shroud connected to andsurrounding all or part of the engine, and may be a fuselage, nacelle, or other portion of the airplane structure. The aft portion of v the shroud extends rearward beyond the exit end of the nozzle to surround and control the exhaust gas stream. Flow passage means, which may be a single peripheral opening or a plurality of discrete openings, aft of the exit end of the nozzle extends through the shroud wall and converges rearward to provide paths for inflow of free stream air during ejector operation and for outflow of the gas stream during reverser operation.

In the presently preferred form a plurality of blocker doors, preferably six, are provided and movably mounted within the aft portion of the shroud. They are substantially flat and generally triangular in planform with an apex at the forward end and a base at the aft end. Each door is pivotally mounted at its.base to the shroud wall and is pivotally mounted at its apex to a common mounting located on the engine axis. The common mounting for the apices is forward of the base mounting so that the axes of rotation of the doors converge forwardly. In stowed positioneach door lies ina radial plane from the engine axis or center line of the shroud, and in fully deployed position each door is swung through an angle of substantially 90 about its FIG. 1 is a schematic side elevational view of a jet engine encased within a shroud incorporating the invention;

FIG. 2 is a schematic view similar to FIG. 1 showing the aft portion of the shroud to a larger scale and including details of the reversing mechanism;

FIG. 3 is a schematic sectional view taken on line 3-- 3 of FIG. 2, portions being broken away;

FIG. 4 is a schematic detail view showing the mounting of the control ring;

FIG. 5 is a schematic detail sectional view further illustrating the relation of the control ring to its mounting track; and

FIG. 6 is a schematic detail view showing the linkage connection between the control ring and one of the blocker doors.

DESCRIPTION OF PREFERRED EMBODIMENT tion of a fuselage of wing or other aircraft structure but for simplicity is shown as having the form of a typical elongate nacelle which is generally annular in cross section and generally coaxial with the engine, and is connected by a pylon 18 to an airplane wing, not shown. The forward portion 20 of the main body of the shroud extends forward or upstream of the compressor to provide a conventional entry passage for the flow of air to the compressor.

The aft portion 22 of the shroud extends rearward beyond the plane of the exit end 24 of the nozzle to define a mixing zone 26. A plurality of passages 28, preferably three, are formed through the wall of the shroud aft of the lateral plane of exit end 24 of the nozzle and are spaced around the periphery between aft portion 22 and the main body 30 of the shroud. Instead of discrete passages, a single passage means may extend in a full circle interrupted only by necessary structure to support the aft portion on the main body. These passages converge rearwardly and extend fully through the wall from the exterior to the interior and provide flow paths for free stream air to enter and join the exhaust gases in the mixing-zone. Thus, portion 22 of the shroud may be considered an ejector barrel. In addition, the same passages form flow paths for thrust reversing outflow of the jet stream when blocker assembly 32 is deployed to prevent the jet stream from flowing axially rearward and diverts it to the passages.

The blocker assembly 32 includes a plurality of blocker doors 34 which are substantially flat, streamlined, and generally triangular in planform, their bases being pivotally mounted in ejector barrel 26 and their apices being pivotally mounted in a common mounting 36 of streamlined form located on the common axis of the shroud and engine. Their axes of rotation may all lie in a single plane perpendicular to said common axis, but preferably the common apex mounting means is forward of the base mounting means so that the axes of rotation of the doors converge forwardly along radial planes from the engine axis, with the presently preferred angle to the axis of the shroud being of the order of 60. With this arrangement, when the doors are rotated approximately 90, their surfaces define a forwardly convex cone which blocks axial rearward flow of the jet stream and diverts it rearward and outward to the passages to reverse the flow direction with a minimum of turbulence and stagnation pockets.

The blocker assembly is shown in greater detail in FIG. 2 where all of the components are the same except that a common mounting 38 is provided in the form of a typical streamlined center body connected to the engine and extending rearward therefrom. An even number of blocker doors 34 is provided. It has been determined that six is the optimum number for reasons of door shape, mounting and operation. It will be noted that the bases 40 of the doors are curved to correspond to the contour of the inner wall 42 of the ejector barrel when the doors are swung about 90 on their axes of rotation from stowed to full blocking position, so that there will be minimum clearance between the bases and the wall.

The apex 44 of each door is provided with an axle 46 mounted in a bearing in common mounting 38, and the base 40 of each door is provided with an axle sleeve 48 rotatably mounted on a shaft, not shown, which is fixed to structural element 50 carried by the wall of the barrel. Thus, each door may swing about its axis of rotation passing through the axles between the stowed position shown in FIGS. 1 and 2 to deployed position, which is about 90 removed and will lie in a plane generally transverse to the engine axis. In such position the bases 40 will mate with wall 42 and the side edges 52 of the doors will mate with each other to define a substantially closed forwardly convex cone to block rearward flow and divert it to passages 28.

The pivotal base mountings for the door are located adjacent to the inner ends of passages 28 as will be seen in FIG. 2. Thus the passages serve as recesses to receive portions of base 40, leaving inner wall 42 of the ejector barrel smooth for more efficient flow. When discrete passages are used, each passage is located and sized to receive the base portions of two adjacent doors. With the mechanism described below, each door swings in the opposite angular sense to the adjacent door on each side; i.e., the doors swing alternately clockwise and counter clockwise. This avoids imparting rotation to the jet stream in any stage of deployment. Also, the doors may be adjusted to and maintained at any selected stage of deployment to produce partial or modulated blockage and reverse thrust effect.

The details of the mechanism for stowing and deploying the blocker doors are shown in FIGS. 4, 5 and 6. A V-shaped channel track 54 extends around the periphery of the ejector barrel 22 and is fixedly mounted to the inner side of its outer wall, as seen in FIG. 4. A control ring 56 extends peripherally inside the track and is provided with a plurality of L-shaped brackets 58, each carrying a roller 60 at its free end. Each bracket extends through a slot 62 in track 54 so that rollers 60 engage the bottom of the track and support the control ring for rotation about the axis of the shroud. Slots 62 are short because the control ring rotates only through a limited angle. An actuator 64 for the ring comprises a servo cylinder 66 pivotally connected to the shroud structure at 68, and a piston rod 70 pivotally connected to the ring at 72. Extension and retraction of the piston rod moves the control ring through an angle corresponding to the length of slot 62. The actuator may be controlled to adjust the ring to any desired rotational position.

The linkage for actuation of doors 34 by the control ring includes a lever 74 fixedly connected to the axle sleeve 48 of each door and provided with a slot 76 at its free end. A control pin 78 is fixedly mounted on the control ring for each door and engages in its respective slot 76. The lever arms are positioned at about 45 to the planes of the doors as best seen in FIG. 6. Rotation of the control ring through a relatively small angle moves each pin 78 peripherally a sufficient distance to swing its lever and the associated door through an angle of about about the axis of rotation of the door. In order to cause adjacent doors to swing in opposite angular senses, the levers are positioned to extend alternately forward and aft, as indicated at the upper and lower locations in FIG. 2.

When the invention is incorporated in a pylonmounted nacelle, as shown, the ejector air passage means may be in the form of a full circle with appropriate bracing means, or may be several discrete passages as preferred. In most cases of installation at the aft end of a fuselage the three-exit type will be indicated because of the proximity of empennage structure. It will be apparent that the invention disclosed herein provides a relatively simple, lightweight, and durable apparatus for providing both full and modulated thrust control in flight and on the ground. While it has been described in relation to a conventional jet engine, it is equally suitable for use in fan jet installations.

Having thus described the invention, what is claimed as new and useful and desired to be secured by US. Letters Patent is:

l. Thrust controlling apparatus for use in combination with a jet engine having a rearwardly discharging nozzle comprising:

and elongate shroud defined by an outer and inner wall of generally annular cross sectional shape comprising a forward main body connected to and surrounding the engine and an aftermost ejector barrel section having a forward and a rearmost portion,

passage means extending through said outer and inner wall terminating at the periphery of said inner wall adjacent the forward portion of said ejector barrel for outflow of exhaust gases to produce reverse thrust,

blocker door apex mounting means co-axially of the engine and in the general zone of the passage means,

a plurality of blocker door base mounting means distributed symmetrically about the shroud at the aft end of the passage means, and

a' plurality of blocker doors each substantially flat and substantially triangular in lanforrn, each door being mounted with its apex pivotally mounted on the apex mounting means and its base pivotally mounted on one of the base mounting means for pivotal movement about an axis lying within a radial plane from the engine axis, and means for swinging the doors in unison about their respective axes between stowed position with each door lying in the radial plane from the engine axis containing the pivotal axis of said each door, and deployed position with each door swung substantially at right angles to its stowed position and with its side edges substantially in contact with the side edges of the doors on each side thereof to block rearward flow of engine gases and redirect them outward through the passage means.

2. Apparatus as claimed in claim 1; the base edge of each door being curved to conform to the contour of the inner wall of the ejector barrel when the doors are in fully deployed position. v v

3. Apparatus as claimed in claim 1; the blocker door apex mounting means comprising astreamlined body spaced aft of the engine.

4. Apparatus as claimed in claim 1; the blocker door apex mounting means comprising a streamlined body connected to the engine and extending rearwardly therefrom.

5. Apparatus as claimed in claim 1; the blocker door apex mounting means being substantially forward of the base mounting means to cause the doors in fully deployed position to form a forwardly convex cone to block rearward flow of gases through the ejector barrel and divert the gases outwardly through the passage means.

6. Apparatus as claimed in claim 5; the axis of rotation of each door being at an angle of the order of 60 to the longitudinal axis of the engine.

7. Apparatus as claimed in claim 5; the base mounting means being located adjacent the inner end of the passage means; the latter serving as a recess to receive portions of the door bases when the doors are in stowed position. v

8. Apparatus as claimed in claim ll; there being an even number of base mounting means substantially equally spaced around the periphery of the shroud inner wall; each door being actuated to swing in an angular sense opposite to the adjoining doors to prevent imparting undesirable rotation to the gas stream.

9. Apparatus as claimed in claim 8; the number of doors being six.

10. Apparatus as claimed in claim 1; the inner and outer ends of the passage means extending completely around the periphery of the shroud to form a single passage.

11. Apparatus as claimed in claim 1; the passage means comprising three discrete passages; the number of doors being six; and portions of the bases of two ad jacent doors extending into each passage in stowed position.

12. Apparatus as claimed in claim 1; and actuator means to move the doors synchronously to any sele'cted position between full stowage and full deployment and to maintain them in such position to produce any desired degree of flow blockage and thrust reversal.

13. Apparatus as claimed in claim 1; a control ring mounted to the ejector barrel substantially surrounding the base mounting means for the doors; actuator means to rotate the control ring about the axis of the shroud; and linkage means connecting the control ring to the doors to cause them to rotate about their axes in response to rotation of the control ring about its axis.

14. Apparatus as claimed in claim 13; the linkage means comprising a lever arm connected to each door adjacent to its base mounting means, and pin-and-slot connections between the lever arms and the control ring.

15. Apparatus as claimed in claim 14; the lever arms on successive doors around the periphery extending alternately forward and rearward to cause successive doors to rotate in opposite angular senses in response to rotation of the control ring in one angular sense.

16. Apparatus as claimed in claim 1; the axes of rotation of the doors converging forwardly toward the engine axis to cause the doors to define a forwardly convex cone in deployed position to divert the gas stream outwardly and rearwardly to the passage means; the base edges of the doors being curved to conform to the contour of the inner wall of the ejector barrel when fully deployed for maximum blockage of the gas stream; a control ring carried by the ejector barrel in substantially the same plane as the base mountings of the doors for rotation about the axis of the shroud; linkage means connecting the doors to the control ring to cause rotation of the doors about their axes in response to rotation of the-control ring about its axis; and actuator means carried by the ejector barrel to cause selective rotation of the control ring.

17. Apparatus as claimed in claim 1, the aft end of each passage means comprising a wall diverging forwardly from the engine axis.

18. Apparatus as claimed in claim 1, the forward and aft ends of each passage means comprising separate walls spaced apart in a fore-and-aft direction and diverging forwardly from the engine axis.

19. Thrust controlling apparatus for use in combination with a jet engine having a rearwardly discharging nozzle and adapted to produce reaction thrust comprising:

an elongate shroud defined by an outer wall and inner wall of generally annular cross sectional shape comprising a forward main body connected to and surrounding the engine and the rearmost section of the shroud comprising an ejector barrel to surround and control the rearwardly issuing exhaust gas stream,

rearwardly converging passage means extending through said outer and inner wall terminating at the periphery of said inner wall between the ejector barrel and the forward main body of the shroud for inflow of free stream air to mix with the engine gases in the ejector barrel and for outflow of engine gases to produce reverse thrust,

a common blocker door mounting at the longitudinal axis of the shroud, and

a plurality of blocker doors located within the barrel for rotation about axes transverse to the longitudinal axis of the shroud, each door being substantially flat and substantially triangular in planform with its base adjacent to the ejector barrel wall and its apex adjacent to the longitudinal axis of the shroud, the base being pivotally mounted in the ejector barrel wall and the apex being pivotally mounted in the common mounting, the doors being swingable between stowed position with each door lying in a longitudinal plane containing the longitudinal axis of the shroud and deployed position with each door lying in a plane transverse to the longitudinal axis of the shroud and with the side edges of the doors substantially in contact with each other to block rearward flow of the exhaust gases and redirect them outward through the passage means with a forward flow component to produce reverse thrust. 

1. Thrust controlling apparatus for use in combination with a jet engine having a rearwardly discharging nozzle comprising: and elongate shroud defined by an outer and inner wall of generally annular cross sectional shape comprising a forward main body connected to and surrounding the engine and an aftermost ejector barrel section having a forward and a rearmost portion, passage means extending through said outer and inner wall terminating at the periphery of said inner wall adjacent the forward portion of saiD ejector barrel for outflow of exhaust gases to produce reverse thrust, blocker door apex mounting means co-axially of the engine and in the general zone of the passage means, a plurality of blocker door base mounting means distributed symmetrically about the shroud at the aft end of the passage means, and a plurality of blocker doors each substantially flat and substantially triangular in planform, each door being mounted with its apex pivotally mounted on the apex mounting means and its base pivotally mounted on one of the base mounting means for pivotal movement about an axis lying within a radial plane from the engine axis, and means for swinging the doors in unison about their respective axes between stowed position with each door lying in the radial plane from the engine axis containing the pivotal axis of said each door, and deployed position with each door swung substantially at right angles to its stowed position and with its side edges substantially in contact with the side edges of the doors on each side thereof to block rearward flow of engine gases and redirect them outward through the passage means.
 2. Apparatus as claimed in claim 1; the base edge of each door being curved to conform to the contour of the inner wall of the ejector barrel when the doors are in fully deployed position.
 3. Apparatus as claimed in claim 1; the blocker door apex mounting means comprising a streamlined body spaced aft of the engine.
 4. Apparatus as claimed in claim 1; the blocker door apex mounting means comprising a streamlined body connected to the engine and extending rearwardly therefrom.
 5. Apparatus as claimed in claim 1; the blocker door apex mounting means being substantially forward of the base mounting means to cause the doors in fully deployed position to form a forwardly convex cone to block rearward flow of gases through the ejector barrel and divert the gases outwardly through the passage means.
 6. Apparatus as claimed in claim 5; the axis of rotation of each door being at an angle of the order of 60* to the longitudinal axis of the engine.
 7. Apparatus as claimed in claim 5; the base mounting means being located adjacent the inner end of the passage means; the latter serving as a recess to receive portions of the door bases when the doors are in stowed position.
 8. Apparatus as claimed in claim 1; there being an even number of base mounting means substantially equally spaced around the periphery of the shroud inner wall; each door being actuated to swing in an angular sense opposite to the adjoining doors to prevent imparting undesirable rotation to the gas stream.
 9. Apparatus as claimed in claim 8; the number of doors being six.
 10. Apparatus as claimed in claim 1; the inner and outer ends of the passage means extending completely around the periphery of the shroud to form a single passage.
 11. Apparatus as claimed in claim 1; the passage means comprising three discrete passages; the number of doors being six; and portions of the bases of two adjacent doors extending into each passage in stowed position.
 12. Apparatus as claimed in claim 1; and actuator means to move the doors synchronously to any selected position between full stowage and full deployment and to maintain them in such position to produce any desired degree of flow blockage and thrust reversal.
 13. Apparatus as claimed in claim 1; a control ring mounted to the ejector barrel substantially surrounding the base mounting means for the doors; actuator means to rotate the control ring about the axis of the shroud; and linkage means connecting the control ring to the doors to cause them to rotate about their axes in response to rotation of the control ring about its axis.
 14. Apparatus as claimed in claim 13; the linkage means comprising a lever arm connected to each door adjacent to its base mounting means, and pin-and-slot connections between the lever arms and the control ring.
 15. Apparatus as claimed in claim 14; the lever arms on sucCessive doors around the periphery extending alternately forward and rearward to cause successive doors to rotate in opposite angular senses in response to rotation of the control ring in one angular sense.
 16. Apparatus as claimed in claim 1; the axes of rotation of the doors converging forwardly toward the engine axis to cause the doors to define a forwardly convex cone in deployed position to divert the gas stream outwardly and rearwardly to the passage means; the base edges of the doors being curved to conform to the contour of the inner wall of the ejector barrel when fully deployed for maximum blockage of the gas stream; a control ring carried by the ejector barrel in substantially the same plane as the base mountings of the doors for rotation about the axis of the shroud; linkage means connecting the doors to the control ring to cause rotation of the doors about their axes in response to rotation of the control ring about its axis; and actuator means carried by the ejector barrel to cause selective rotation of the control ring.
 17. Apparatus as claimed in claim 1, the aft end of each passage means comprising a wall diverging forwardly from the engine axis.
 18. Apparatus as claimed in claim 1, the forward and aft ends of each passage means comprising separate walls spaced apart in a fore-and-aft direction and diverging forwardly from the engine axis.
 19. Thrust controlling apparatus for use in combination with a jet engine having a rearwardly discharging nozzle and adapted to produce reaction thrust comprising: an elongate shroud defined by an outer wall and inner wall of generally annular cross sectional shape comprising a forward main body connected to and surrounding the engine and the rearmost section of the shroud comprising an ejector barrel to surround and control the rearwardly issuing exhaust gas stream, rearwardly converging passage means extending through said outer and inner wall terminating at the periphery of said inner wall between the ejector barrel and the forward main body of the shroud for inflow of free stream air to mix with the engine gases in the ejector barrel and for outflow of engine gases to produce reverse thrust, a common blocker door mounting at the longitudinal axis of the shroud, and a plurality of blocker doors located within the barrel for rotation about axes transverse to the longitudinal axis of the shroud, each door being substantially flat and substantially triangular in planform with its base adjacent to the ejector barrel wall and its apex adjacent to the longitudinal axis of the shroud, the base being pivotally mounted in the ejector barrel wall and the apex being pivotally mounted in the common mounting, the doors being swingable between stowed position with each door lying in a longitudinal plane containing the longitudinal axis of the shroud and deployed position with each door lying in a plane transverse to the longitudinal axis of the shroud and with the side edges of the doors substantially in contact with each other to block rearward flow of the exhaust gases and redirect them outward through the passage means with a forward flow component to produce reverse thrust. 